1. Field of the Invention
The present invention relates to a process of producing a room temperature curable organopolysiloxane that can be easily cured with moisture to form a rubberlike elastic cured product, and more particularly to a process of producing a room temperature curable organopolysiloxane composition which is effectively inhibited from slumping before it is cured.
2. Description of the Prior Art
Hitherto, room temperature curable organopolysiloxane compositions that can easily be cured with moisture to form a rubberlike elastic cured product are widely used, for example, for adhesives, coating materials, electrical insulating seal materials, and sealing materials for industry and construction. Among these, the case where they are used for sealing materials for industry and construction requires that the composition will not slump before the composition is cured.
To obtain such a composition which will not slump, generally a slump preventive is added. As the slump preventive, for example, a polysiloxane having phenyl groups (U.S. Pat. No. 4,100,129), a polyoxyalkylene compound (Japanese Pre-examination Patent Publication (kokai) No. 56.853 (1981), and a polyoxyalkylene compound having a hydrolyzable silicon-containing organic group at an end of the molecule (Japanese Pre-examination Patent Publication (kokai) No. 62-135560 (1987) are known.
However, the above-mentioned slump preventives are poor in compatibility with organopolysiloxanes that are base polymers of the compositions and are accompanied by a problem that they lower the transparency of the compositions. Further, where these slump preventives are used, it is needed that the surface of a finely divided silica used as a filler is treated with an organosilicon compound such as a dimethydichlorosilane and therefore a disadvantage of a higher cost cannot be evaded. That is, if untreated finely divided powder silica that is low in cost is used as a filler, there is a problem that the effect of slump prevention cannot be exhibited fully.
Also, methods for obtaining a room temperature curable composition which will not slump without using a slump preventive is known, and, for example, Japanese Pre-examination Patent Publication (kokai) No. 02-41361 (1990) suggests a method wherein an organopolysiloxane having hydroxyl groups is mixed previously with a crosslinking agent, and thereafter the resulting mixture is mixed with a finely divided powder silica, a curing catalyst, etc.
However, the above-mentioned method of obtaining a room temperature curable composition without using a slump preventive can only be applied to an oxime-elimination type composition, the obtained composition is poor in transparency and the shelf stability is unsatisfactory.